Vectors, Hosts, and Assembly Architectures

Manual: General · Subject: Genetic Cloning

Compare cloning vectors, host organisms, and modern assembly frameworks used to build recombinant DNA constructs.

Vector Classes

Plasmids, phage, BACs, and YACs

Plasmids are the most common cloning vectors because they are compact, easy to manipulate, and often high copy. Larger inserts may require bacteriophage-derived vectors, bacterial artificial chromosomes (BACs), or yeast artificial chromosomes (YACs), each offering different capacities and stability profiles.

Common vector platforms

Plasmid vectors

Small insert capacity
Simple propagation and screening
Often best for routine subcloning

BACs/YACs

Large insert capacity
Useful for genomic libraries
Typically lower throughput and greater handling complexity

Hosts and Compatibility

Host selection

Host choice is dictated by replication origin compatibility, transformation efficiency, post-translational modification needs, and biosafety constraints. Common hosts include Escherichia coli, yeast, insect cells, and mammalian cells.

Design constraints

Host range

Species or strain in which the vector can replicate

Copy number

Average number of vector molecules per cell

Insert burden

Metabolic or structural cost imposed by the construct

Genetic stability

Likelihood the construct remains intact through growth

Which vector type is generally preferred for very large genomic inserts?

Simple cloning plasmid BAC Small expression plasmid Synthetic oligonucleotide

A vector with a yeast origin of replication but an E. coli antibiotic marker would be considered primarily a

single-host vector bacterial genome shuttle vector suicide vector

Assembly Frameworks

Restriction-ligation and seamless assembly

Classical cloning uses restriction digestion and ligation, while seamless assembly methods such as Gibson assembly, Golden Gate, and homologous recombination-based strategies reduce dependence on unique restriction sites and support modular, multi-part construction.

Why are seamless assembly methods attractive for multi-part constructs?

Which feature most directly supports constructing multi-fragment assemblies with defined order?

Random mutagenesis Type IIS restriction enzyme-based design Auxotrophic selection alone Pulse-field electrophoresis

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